Many of recent digital cameras are equipped with a camera shake correction function. Configurations for realizing this camera shake correction function can be classified into an electronic type and an optic type. The optic type compensates camera shake by moving a lens and an imaging device, while the electronic type compensates camera shake by superimposing plural images taken by continuous shooting so as to align the images. The electronic type has been incapable of compensating blurring of images occurred within 1/30 second because the conventional frame rate of most imaging devices is 30 frames per second. However, such a defect is overcome now by using the imaging device having high-speed frame rate of 1.2 mega 300 frames per second that has been developed by Sony Corporation.
When an electronic type of camera shake correction is performed using such an imaging device of high speed frame rate, high speed continuous shooting is performed in one image taking operation and the motion vector of each of plural shot images are detected. Based on the detected motion vector, the shot images are superimposed upon each other to correct blurring. More specifically, as whole of the imaging area on the imaging device cannot be used, an area having a predetermined size smaller than the whole imaging area is set as a record area. On the record area, the shot images are superimposed upon each other so as to be aligned (see for example, Japanese Patent Application Publication Nos. 11-252445, 2000-341577, and 2005-130159). According to these techniques, an image of appropriate light amount can be obtained by superimposing plural shot images.
Incidentally, there has been proposed a technique in which a flash is emitted for one operation of continuous shooting, thereby taking an image brighter than an image without a flash (see, for example, Japanese Patent Application Publication Nos. 2007-36978, 2007-49374, and 2003-304443). More specifically, Japanese Patent Application Publication Nos. 2007-36978, and 2007-49374 propose the technique in which two images are taken in one operation of continuous shooting: the first image taken with a flash and the second image taken without a flash are superimposed so that an image that has appropriate exposure and is brighter than an image taken without a flash can be taken. In addition, Japanese Patent Application Publication No. 2003-304443 proposes the technique in which the difference in light amount between the images taken with and without a flash is obtained to correct irradiation distribution of the flash; image data only for the shot image with flash is created and subjected to correction for light unevenness so that distribution of light amount is made even over the whole of the image and the image with appropriate exposure can be obtained. The technique disclosed in Japanese Patent Application Publication Nos. 2007-36978, 2007-49374, and 2003-304443 is applied to slow synchronized image taking and the like. As camera shake is easily occurred in slow synchronized image taking, if the technique disclosed in Japanese Patent Application Publication Nos. 2007-36978 and 2007-49374 is combined with the technique of electronic camera shake function, an image that is corrected for camera shake and brighter than an image shot without a flash can be obtained. In addition, if the technique disclosed in Japanese Patent Application Publication No. 2003-304443 is combined with a technique with electronic camera shake function, it is possible to prevent a case in which the light amount on the perimeter of an image is decreased compared to that of the center of the image.
However, none of Japanese Patent Application Publication Nos. 2007-36978, 2007-49374, and 2003-304443 describes details as to how to adjust the light amount of a flash in order to obtain an image with appropriate exposure.